Power and Energy

Author: Solar 4 RVs  

Understanding Power and Energy for Your Solar System

Choosing the right solar system requires understanding your power and energy consumption. While these terms are often used interchangeably, they refer to different aspects of electricity use.

Power refers to the instantaneous rate at which an appliance or device, like a lamp or a kettle, consumes energy. This is often expressed in watts. On the other hand, energy refers to the total amount of electricity consumed over time, often measured in watt-hours (Wh). While an appliance might maintain a constant power level, the total energy used increases the longer the device runs.

Therefore, when choosing a solar power system for your RV or marine vessel, you must consider:

  • Power needs: How many appliances/devices you use simultaneously, i.e., the energy drawn at once. - Important for an inverter size!
  • Energy needs: The duration of appliance use in a day, i.e., the total energy consumed that drains your battery reserve. - Important for battery capacity!

A watt (W) is a unit of power, while a watt-hour (Wh) is a unit of energy. One watt-hour represents the energy consumed by a one-watt device running for one hour. Similarly, 1000W equals one kilowatt (kW), and 1kWh equals 1000 watt-hours of energy.

  • Power: If your appliance draws 1000W (say a small kettle), then you will need a 1000W+ inverter.
  • Energy: If your appliance draws 1000W for 3 hours, then you will need 1000W x 3h = 3000Wh of energy storage, if a 12V system, 3000Wh / 12V = 250Ah

To determine the right solar power system, we'll consider the power rating of your appliances and their usage duration.

Calculating Watt-Hours for Appliances/Devices

Link to how to calculate watt hours

View our comprehensive list of common appliance wattages and learn how to calculate their energy consumption in watt-hours.